Thread: Guys, really need your help

It doesn't show any mistake before I launch it, but after I've entered the number I wanted to generate, it showed me this mistake


Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException… -3(sometimes -4, or -6 etc.)
at pratice.main(pratice.java:16)

Did you find any mistake in the code? Please, I have to show it tomorrow

The Random's nextInt() could return negatives. However, this might work for you.

r.nextInt(Integer.MAX_VALUE)%10;

However, if that generated 1000 and then 100, it would both go to 0 with that mod 10.

You could just actually use

r.nextInt(10); which would get numbers between 0 inclusive and 10, exclusive.

Again, however, you can't control which random number it picks.

Math.random() returns a double between 0, inclusive I think, and 1, exclusive I am pretty sure.

So you could have

(int) (Math.random() * 10) ;

import java.util.*;
public class xyz
    {
    public static void main(String [] args)
         {
               Scanner S=new Scanner(System.in);
               System.out.println("Enter how many random numbers you want to generate");
               int N=S.nextInt();
               Random r = new Random();
               int [] freq = (int) (Math.random() * 10); // <----- [COLOR="#B22222"][COLOR="#B22222"]cannot convert from int [] to int[/COLOR][/COLOR]
 
               for(int i=0;i<10;i++)freq[i]=0;
 
               for(int i=0;i<N;i++)
                    {
                      int k=r.nextInt()%10;
                      freq[k]++;
                     }
               for(int i=0;i<10;i++)
                    { 
                      for(int j=0;j<freq[i];j++)System.out.print("*");
                      System.out.println();
                    }
 
         }
    }

Norm,

int [] freq = (int) (Math.random() * 10); // cannot convert from int[] to int

this is the only mistake.. is it possible to fix this??

Originally Posted by Norm

On the left of the = is a definition for an int array
on the right is a single int value.

The compiler won't like doing that assignment. It wants the same types on both sides of the =

What are you trying to do in that statement?

//Don't you mind to show me how to fix this?
//the last line was just a comment

Yes! I changed it to

int freq = (int) (Math.random() * 10);

import java.util.*;
public class xyz
    {
    public static void main(String [] args)
         {
               Scanner S=new Scanner(System.in);
               System.out.println("Enter how many random numbers you want to generate");
               int N=S.nextInt();
               Random r = new Random();
               int freq =  (int) (Math.random() * 10);
 
               for(int i=0;i<10;i++)freq[i]=0;  // it shows mistake here
 
               for(int i=0;i<N;i++)
                    {
                      int k=r.nextInt()%10;
                      freq [k]++; // it shows mistake here
                     }
               for(int i=0;i<10;i++)
                    { 
                      for(int j=0;j<freq[i];j++)System.out.print("*"); // it shows mistake here
                      System.out.println();
                    }
 
         }
    }

So now it shows me mistakes,

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
The type of the expression must be an array type but it resolved to int
The type of the expression must be an array type but it resolved to int
The type of the expression must be an array type but it resolved to int

Array indexes aren't valid, unless your variable happens to be of type Object, then it could be I think, if you initialized it as such, for regular int type.

Try using a different variable than freq for that:

int freq = (int) (Math.random() * 10);

Try this instead perhaps:
int[] freq = new int[10];

int freq2 = (int) (Math.random() * 10);

That should get rid of those compiler errors you just posted.

Now I don't see any mistakes, except after I enter the numbers

[java=code]freq [k]++; // it shows mistake here[/code]

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -5
at xyz.main(xyz.java:17)

r.nextInt() will return some random number that is a valid integer. That's from -2^32 +1 to 2^32 -1 I think. However, you could keep it as it but do this

int k = Math.abs(r.nextInt()) % 10;

That takes the absolute value of it.

or you could do

int k = r.nextInt(10);

I'm not sure if it's doing what you wanted it to, but this code below will compile and, at least that I'm aware of, has no runtime errors.

import java.util.*;
public class xyz
    {
    public static void main(String [] args)
         {
               Scanner S=new Scanner(System.in);
               System.out.println("Enter how many random numbers you want to generate");
               int N=S.nextInt();
               Random r = new Random();
					int[] freq = new int[10];
               int freq2 =  (int) (Math.random() * 10);
 
               for(int i=0;i<10;i++)freq[i]=0;  // it shows mistake here
 
               for(int i=0;i<N;i++)
                    {
                      int k=r.nextInt(10);
                      freq [k]++; // it shows mistake here
                     }
               for(int i=0;i<10;i++)
                    { 
                      for(int j=0;j<freq[i];j++)System.out.print("*"); // it shows mistake here
                      System.out.println();
                    }
 
         }
    }

That's awesome, look at the output:

[java=code]
Enter how many random numbers you want to generate
100
0. ***********
1. *************
2. ********
3. ****
4. *********
5. ***************
6. **********
7. ******
8. *****************
9. *******
[/code]

Originally Posted by javapenguin

r.nextInt() will return some random number that is a valid integer. That's from -2^32 +1 to 2^32 -1 I think. However, you could keep it as it but do this

int k = Math.abs(r.nextInt()) % 10;

That takes the absolute value of it.

or you could do

int k = r.nextInt(10);

I'm not sure if it's doing what you wanted it to, but this code below will compile and, at least that I'm aware of, has no runtime errors.

import java.util.*;
public class xyz
    {
    public static void main(String [] args)
         {
               Scanner S=new Scanner(System.in);
               System.out.println("Enter how many random numbers you want to generate");
               int N=S.nextInt();
               Random r = new Random();
					int[] freq = new int[10];
               int freq2 =  (int) (Math.random() * 10);
 
               for(int i=0;i<10;i++)freq[i]=0;  // it shows mistake here
 
               for(int i=0;i<N;i++)
                    {
                      int k=r.nextInt(10);
                      freq [k]++; // it shows mistake here
                     }
               for(int i=0;i<10;i++)
                    { 
                      for(int j=0;j<freq[i];j++)System.out.print("*"); // it shows mistake here
                      System.out.println();
                    }
 
         }
    }

When I find out when neg repped me like that, they are DEAD!

I was NOT spoonfeeding. That code was a copy/paste pretty much of their own code a few posts earlier.

I've reported the incident to the Administrator.

Thank you for help javapenguin and Norm! I really appreciate it... I learn a lot from both of you guys.

Can anybody explain me why javapenguin ws banned?